On the recent mobile phone market, types of mobile phones having built-in camera modules have been dominant. These camera modules are meant to be embedded in the mobile phones. Therefore, they face greater demands for being compact and lightweight, compared with camera modules to be embedded in digital cameras.
Also, there have been an increasing number of camera modules that (i) operate their autofocus (AF) systems with the use of lens drive devices and (ii) are mounted on electronic devices such as mobile phones. Examples of lens drive devices that have been developed so far encompass those employing stepper motors, piezoelectric sensors, and VCM (Voice Coil Motor). Such lens drive devices have already been distributed on the market.
Meanwhile, now that such camera modules having autofocus systems have become new standards, a system for compensating for hand shake is becoming the focus of attention as a next distinctive feature. Although a system for compensating for hand shake has been widely used for digital cameras and camcorders, there have been only a few mobile phones equipped with systems for compensating for hand shake, due to the issue of a limited size of mobile phone. Nevertheless, it is expected that mobile-phone-specified camera modules having systems for compensating for hand shake will be more widespread in years to come, and, in fact, a new system (configuration) for compensating for hand shake, which can be made compact, has been suggested.
Patent Literature 1 discloses, as a system for compensating for hand shake, a camera-shake correction device employing a “barrel shift” format. The camera-shake correction device disclosed in Patent Literature 1 is, in order to move a lens barrel in accordance with the optical axis, a camera-shake correction device that stabilizes an image by moving the entire auto-focusing lens drive device or its moving part in a first direction and a second direction which are perpendicular to the optical axis and are perpendicular to each other, the auto-focusing lens drive device being provided with a focusing coil and a permanent magnet which is disposed on the outside of the focusing coil. The camera-shake correction device includes: a base disposed to be spaced from the bottom surface of the auto-focusing lens drive device; a plurality of suspension wires which each have one end fixed to the outer peripheral section of the base, which extend along the optical axis, and which support the entire auto-focusing lens drive device or its moving part in such a manner that the auto-focusing lens drive device can rock in the first direction and the second direction; and a camera-shake correcting coil disposed to face the permanent magnet.
Also, Patent Literature 2 discloses a technology for increasing a shock resistance feature of a device for compensating for hand shake, which device employs a suspension wire similar to the one disclosed in Patent Literature 1. A lens drive device disclosed in Patent Literature 2 includes: a first supporting body that hold the lens and is capable of moving in the direction of the optical axis; a second supporting body that holds the first supporting body in a manner enabling movement in the direction of the optical axis; a fixed body that hold the second supporting body in a manner enabling movement in directions that are roughly perpendicular to the direction of the optical axis; a first drive mechanism for driving the first supporting body in the direction of the optical axis; a second drive mechanism for driving the second supporting body in a predetermined first direction that is roughly perpendicular to the direction of the optical axis; a third drive mechanism for driving the second supporting body in a second direction that is roughly perpendicular to the direction of the optical axis and to the first direction; a plurality of wires for connecting the second supporting body to the fixed body; and a buckling prevention member for preventing buckling of the wires. The wires are formed linearly; the second supporting body is supported by the fixed body by means of the wires in a manner enabling movement in directions that are roughly perpendicular to the direction of the optical axis; and the buckling prevention member is made of elastic material, and is elastically deformed in the direction of the optical axis by a force smaller than the buckling load of the wires.